1. Field of the Invention
This invention relates generally to the development of interactive visual media, and, more specifically, to improvements in systems used in the development (“authoring”) of media content for delivery in the DVD-Video and other multi-media formats.
2. Background Information
The DVD-Video format is one of a number of formats, both standardized and proprietary, within the general category of interactive multimedia. These formats are capable of presenting motion or still images, along with accompanying sound, to an enduser (viewer) on a display such as a television screen or a computer monitor. The media are referred to as “interactive” because they allow the timing, order, and conditions governing presentation to vary depending on input from the end-user.
In a typical DVD-Video playback setting, user input is communicated to the playback device via either a remote control (as for a set-top DVD-Video player) or a computer mouse and keyboard (as for a DVD-ROM drive connected to a computer). The user responds to on-screen prompts or menus (lists of possible options) by pressing keys or clicking the mouse. The playback path through the material available to be played is altered according to the choices or “navigation” of the user.
When presenting DVD-Video program material, a DVD playback device works with two basic categories of data to create the experience of the end-user. Presentation data is the data that is actually seen or heard: the video, audio, graphics and text. Logical or control data is information about the order and conditions under which presentation data is presented. Logical data defines the way the content is organized, and also the way in which user input will affect the navigational flow through the presentation data. The details of the various aspects of the DVD storage means and protocol are described more fully in “DVD specification for Read-Only Disc, Physical, File Format and Video Specifications”, DVD Consortium, 1997, which is hereby incorporated by reference in its entirety.
The process of creating interactive multimedia is generally referred to as “authoring.” Authoring is usually accomplished using one or more software applications running on a computer. In DVD-Video authoring, a disc or collection of discs that are created to be a single unit is commonly referred to as a “DVD title.” The authoring work in progress on a given title is commonly referred to as a “project.”
The heart of authoring is the defining of the logical data used to structure the playback of presentation data, such as defining the “user interface” (e.g. menus) used to navigate the program, the choices offered to users during playback, and the response of the playback device to user input. During this process, the project's presentation data is normally stored on a hard-drive where it is accessible—locally or via a network—to the authoring system. This allows the author to review the effects of authoring decisions on the way in which the program material is presented.
During the process of defining a project's logical data, the presentation data to which the logical data refers may be in any file format supported by the authoring software, and may be stored at any accessible location. In a project using multiple video clips, for instance, the source file for one clip might be an .AVI file stored on the authoring system's internal hard-drive, for another it might be an MPEG-2 file on an external hard-drive, and for a third it might be a QuickTime file accessed from a server over a network.
Each authoring program has its own method of keeping track of the location and format of the presentation files used in a given project, and also keeping track of the logical data decisions that are made during authoring. One such approach is AuthorScript, developed by Sonic Solutions and used in several of its authoring programs. Other approaches are described, for example, in International Patent Application WO 99/38098, published 29 Jul. 1999, and U.S. Pat. No. 6,023,713, both of which are hereby incorporated by reference. In the AuthorScript approach, an AuthorScript (.AS) authoring file is created by the authoring program to store both “structure” information related to a project's logical data, and “asset” information about a project's presentation data. Further aspects relating to the production of interactive optical media are described International Patent Application WO 96/15500, May 23, 1996, and related U.S. patent application Ser. No. 676,121, both of which are also hereby incorporated by reference.
This process is shown schematically in FIGS. 1 and 2. FIG. 1 is a flow chart with file being opened in steps 101-105, the editing process in steps 107-109, the formatting processing in steps 111-119, and the disc image is written in step 121.
When an existing project is “opened” (or a new authoring file started) in step 101, the project file, for example the AS file in an AuthorScript-based authoring program, is read and the asset information in it is used to locate the source files of the presentation data in step 103. The structure data, meanwhile, is used in step 105 to restore the project's logical state. Step 105 need not be subsequent to step 103, but can occur before or overlap step 103.
As the project is edited (steps 107-109), new assets can be added in step 108 and changes are stored in the project file in step 109, making an up-to-date record of the author's progress on the project.
At the end of the authoring process, when all the decisions regarding logical data are finalized, the project is formatted for delivery on a DVD in steps 111-119. In step 111, the formatting software reads the project file, evaluates the information therein, and carries out a series of operations that convert the project's current state into a form that is playable from a DVD-Video playback device.
In terms of presentation data, in step 113 the process first involves locating the various source files referenced in the project file and, where necessary, converting those files in step 115 to “elemental streams,” which are files in the formats used by DVD-Video for the various types of presentation media (e.g. video source files that are not already in the MPEG-2 video format are converted to that format). This may involve “transcoding” of one or more video files (e.g. a complete feature film) from one format to another. In some cases, it may also involve “compositing” several distinct components found in separate files into a unified whole in step 117. Compositing is particularly common in the case of menus, which often involve a number of visual elements that reside in different files during the authoring process.
With the elemental streams existing in the appropriate file formats for use in DVD, they can then be multiplexed together at step 119 into the Video Object files that are used by a DVD playback device. The logical data created in authoring is also organized into a set of files that can be read and interpreted by a playback device designed to play back discs in the DVD-Video format. Then a “disc image” is written in step 121 that embodies the entire directory structure and data files that will appear on the final disc, with the logical and presentation files all residing in a VIDEO_TS directory (the “DVD-Video zone”, or, more generally, the “authored content zone”), from which they can be read by a DVD-Video playback device.
FIG. 2 is a block diagram representing the various elements of this process. The workstation 201 used for the authoring process contains the authoring file 210 with the project's structure information 211 and asset information 213. The source files can either be stored on the workstation internal hard drive 225 or at external source 223. When the editing process is finished, the Video Object files are formed at formatting 230 and the disc image, containing the logical and presentation data, is supplied to the disc writer 240 and placed onto the disc 250.
A disc image is the source for all the DVDs that are made of a given title, whether replicated in a DVD plant or recorded onto a recordable DVD medium. However, the disc image cannot itself be opened as a project in a DVD-Video authoring program. A DVD-Video disc, therefore, is not functionally equivalent to the project from which it was made, and any subsequent changes to the project can currently only be accomplished by going back to the project file and the source assets it references.